There are wide variety of spools available for carrying relatively heavy loads of wire, cable and the like. Spools for heavy load applications have traditionally been manufactured from such materials as sheet metal, plastic, wood, and cast iron. From the economic standpoint of material, transportation and assembly costs, it is particularly advantageous to provide such a spool made from sheet metal. Sheet metal has a characteristic of being relatively rigid while being relatively thin which allows the separate sheet metal components of the spool to be fabricated at a metal manufacturer, shipped closely together in large volume to a wire or cable manufacturer, and assembled at the plant of the wire or cable manufacture for receipt of wire or cable. Conventional sheet metal spools have been manufactured relatively inexpensively from either three-pieces or five-pieces of separate sheet metal components. It is also known to provide more complex sheet metal spools made from more pieces, however, more complex sheet metal spools diminish the economic cost advantages of three-piece and five-piece spools.
Five-piece spools typically comprise a cylindrical barrel upon which wire is wound, and a pair of two-piece flange sub assemblies disposed at respective ends of cylindrical barrel. Each flange sub assembly includes two pieces including a generally disc-shaped outer flange having a central opening, and a flange hub disposed in the opening and joined to the flange by a loose curl. Each flange sub assembly is secured to the cylindrical barrel by a tightened curl formed of closely interfitting curled metal edges of the flange hub, the flange and the cylindrical barrel. The tightened curl achieves a relatively rigid, high strength spool that is capable of carrying large loads of wire or cable and capable of being stacked and transported without falling apart or disassembling. Usually, the cylindrical barrel and the flange sub assembly are formed at the metal fabrication plant which allows the cylindrical barrels and flange sub assemblies to be shipped closely together thereby minimizing void space during transport. Then the final assembly of the cylindrical barrels to the flange sub assemblies occurs at the plant of the wire or cable manufacturer where wire or cable is subsequently wound onto the fully assembled spool.
One problem with prior five-piece metal spools is that the ability to transfer torque between different spool components of a fully assembled spool is relatively poor, particularly between the flange hub and the flange. The ability to transfer torque is highly desired for wire winding or pulling functions in which wire or cable is wound tightly onto the spool typically by applying a rotational force to drive holes in the central flange hub. For a fully assembled five piece spool having a 1 and 15/16 inch diameter barrel, the tightened curl of the spool has typically only achieved between about 60 inch-lbs. and a maximum of about 100 inch-lbs. of torque load transfer (with a mean average of about 90 inch-lbs.) between the flange hub and the outer flange, using a test of applying a torque wrench to the flange hub through the drive holes while holding the outer flange fixed. However, in some applications, industry desires much higher torque load transfers between the flange hub and the outer flange, typically for wire winding or pulling functions, which makes prior five-piece metal spools insufficient for those applications.
To avoid torque load transfer problems associated with prior five-piece metal spools, industry has used three-piece metal spools in certain applications having a high torque load requirement. Three-piece metal spools typically comprise a cylindrical barrel upon which wire is wound, and a pair of flanges disposed at respective ends of cylindrical barrel. To connect the flanges to the cylindrical barrel, the cylindrical barrel includes tabs which are fit through punched out holes in the flanges. The tabs are crimped to the flanges to secure the flanges to the cylindrical barrel. Although the tab and hole mechanism provides sufficient torque transfer, three-piece spools have suffered from other strength disadvantages. More specifically, when three-piece spools carry heavy loads of wire or cable, the tabs tend to dislodge from the holes causing the flanges to pull away from the cylindrical barrel. This is especially problematic when stacking and transporting multiple three-piece spools loaded with wire or cable. The flanges of the three-piece spools can collapse under heavy loads which allows wire or cable to fall off the cylindrical barrel which in turn results in wasted wire or cable product.